This invention relates to digital television data links pursuant to CCIR 601 standard and particularly to a means by which signals representative of a high-definition, wide-aspect-angle image may be transmitted over a transmission system having characteristics in accordance with CCIR standard 601.
Standard 601 promulgated by the CCIR (International Radio Consultative Committee) defines a 2-channel component (as opposed to composite) digital television system with a 13.5 MHz channel rate in which each 63.5 .mu.S horizontal line includes 720 samples or pixels in each channel, for a total of 1440 pixels per line. According to the standard, the 720 pixels of one channel are allocated to luminance information, and 360 of the pixels in the other channel are allocated to R-Y, with the remaining 360 pixels allocated to B-Y.
The above standard has been in preparation for several years, and it is expected that digital data processors and videotape recorders pursuant to the standard will become available in the near future.
There has been a recent surge of interest in television systems having high definition (highdef or HDTV) and aspect ratios greater than 4:3 (wide angle) which are compatible with conventional standard-definition (standef) 4:3 receivers. While special processing is required to produce wide-angle highdef signals compatible with conventional receivers, as described in U.S. Pat. No. 4,429,327 issued Jan. 31, 1984 to Oakley et al. and in U.S. patent application Ser. No. 350,088 filed Feb. 2, 1982, which issued Nov. 5, 1985, as U.S. Pat. No. 4,551,754 to W. H. Meise et al. there is need for processing such signals in the television studio with modern equipment. The most up-to-date equipment expected to be available shortly is digital equipment pursuant to CCIR standard 601.
There are two major television standards in use in the world; those having 625 lines-per-field at a 50 Hz field rate (625/50), and those having 525 lines-per-field at a 60 Hz field rate (525/60). In a 525-lines-per-frame television picture, 21 television lines (TVL) of each of two fields are used for blanking and are therefore not available for active picture information, with the result that there are 483 active lines, representing pixels in the vertical direction. Assuming that it is desired to have equal vertical and horizontal definition, each pixel is "square", and a standef 4:3 (4 units horizontally, 3 units vertically) aspect ratio picture may be said to have EQU 4/3.times.483=644 pixels
in the horizontal direction. Similarly, a wide-angle or wide-aspect-ratio standef picture having a 5:3 aspect ratio would then have EQU 5/3.times.483=805 pixels
in the horizontal direction. This may be rounded to 800 horizontal pixels if the assumption is made that for "square" pixels this corresponds to 480 active lines in the vertical direction, which in turn corresponds to or requires 22.5 TVL/field of blanking.
A high-definition television picture is usually considered to provide a 2:1 improvement in definition both horizontally and vertically. Beginning from a wide-angle standef picture of 800 horizontal pixels and 480 active lines per frame, a wide angle highdef system requires 1600 horizontal pixels and 960 lines per frame at 30 frames-per-second (actually 30/1.001) for the luminance component, and 800 pixels by 480 lines for the R-Y component (C.sub.R) and for the B-Y component (C.sub.B). It would be very desirable to be able to transmit such a high definition wide angle signal in a format which simulates the format of CCIR 601 so that the signal could be processed, transmitted and/or recorded by equipment pursuant to the standard.